GSM Network time synchronization for RTC using AT+CLTS command
Since I started designing the VALTRACK GPS trackers, I have always had trouble maintaining the tracking device’s correct time because once I removed the battery, the PIC RTC lost its synchronization. I didn’t have the space or luxury to maintain a separate backup battery for the PIC RTC.Â
So, I only used the server time for the incoming packets where the time field was auto-populated by the server-side script.
This method was ok for certain applications but we didn’t have the method to know the delayed packet time (Which gets re-sent later on failure). This is when I was looking for a method to calibrate and sync the MCU RTC to the right time on power-on reset.Â
Table of Contents
Sync using network time :
We then implemented this method where in the GSM module synchronizes its internal RTC and then we take the clock value of the GSM module and set the clock of our PIC RTC
This method has been working fine so far as it doesn’t need any manual intervention for calibrating the time.
Here are the commands I used:
Command to read the GSM RTC clock :
ATE1 Set Command Echo Mode
ATE1
ATI Display Product Identification Information
ATI
AT+CREG Network Registration
AT+CREG=1
AT+CSQ Signal Quality Report
AT+CSQ
AT+COPS Operator Selection
AT+COPS?
AT+CMGF Select SMS Message Format
AT+CMGF=1
AT+CCLK Clock
AT+CCLK?
AT+CLTS Get Local Timestamp
AT+CLTS=1
AT&W Store Active Profile
AT&W
Final code
/*
* File: main.c
* Author: Devilal
*
* Created on 31 March 2021, 4:08 PM
*/
#define FCY 10000000UL // Instruction cycle frequency, Hz - required for __delayXXX() to work
#include "stdio.h"
#include "stdlib.h"
#include "string.h"
#include "libpic30.h"
#include "xc.h"
// CONFIG3
#pragma config WPFP = WPFP511 // Write Protection Flash Page Segment Boundary (Highest Page (same as page 85))
#pragma config WPDIS = WPDIS // Segment Write Protection Disable bit (Segmented code protection disabled)
#pragma config WPCFG = WPCFGDIS // Configuration Word Code Page Protection Select bit (Last page(at the top of program memory) and Flash configuration words are not protected)
#pragma config WPEND = WPENDMEM // Segment Write Protection End Page Select bit (Write Protect from WPFP to the last page of memory)
// CONFIG2
#pragma config POSCMOD = XT // Primary Oscillator Select (XT oscillator mode selected)
#pragma config IOL1WAY = ON // IOLOCK One-Way Set Enable bit (Write RP Registers Once)
#pragma config OSCIOFNC = OFF // Primary Oscillator Output Function (OSCO functions as CLKO (FOSC/2))
#pragma config FCKSM = CSDCMD // Clock Switching and Monitor (Both Clock Switching and Fail-safe Clock Monitor are disabled)
#pragma config FNOSC = PRI // Oscillator Select (Primary oscillator (XT, HS, EC))
#pragma config IESO = OFF // Internal External Switch Over Mode (IESO mode (Two-speed start-up) enabled)
// CONFIG1
#pragma config WDTPS = PS32768 // Watchdog Timer Postscaler (1:32,768)
#pragma config FWPSA = PR128 // WDT Prescaler (Prescaler ratio of 1:128)
#pragma config WINDIS = OFF // Watchdog Timer Window (Standard Watchdog Timer is enabled,(Windowed-mode is disabled))
#pragma config FWDTEN = OFF // Watchdog Timer Enable (Watchdog Timer is enabled)
#pragma config ICS = PGx3 // Comm Channel Select (Emulator functions are shared with PGEC3/PGED3)
#pragma config GWRP = OFF // General Code Segment Write Protect (Writes to program memory are allowed)
#pragma config GCP = OFF // General Code Segment Code Protect (Code protection is disabled)
#pragma config JTAGEN = OFF // JTAG Port Enable (JTAG port is disabled)
//void delay(int delay);
int gsm_index,uart2_index,uart3_index,uart4_index;
char gsm_buffer[100],uart2_buffer[100],uart3_buffer[100],uart4_buffer[100];
int gsm_year,gsm_month,gsm_date,gsm_hours,gsm_minutes,gsm_seconds;
char GSM_TIME_DATE[128];
char pkz[4];
void UART1Init(void)
{
// U1BRG = 25; // 9600 @ 8MHZ
U1BRG = 32; // 9600 @ 10MHZ
U1MODEbits.UARTEN = 1; // UART2 is Enabled
U1MODEbits.USIDL = 0; // Continue operation at Idlestate
U1MODEbits.IREN = 0; // IrDA En/Decoder is disabled
U1MODEbits.RTSMD = 0; // flow control mode
U1MODEbits.UEN1 = 0b00; // UTX, RTX, are enabled U1CTS, U1RTS are disabled
U1MODEbits.UEN0 = 0b00; // UTX, RTX, are enabled U1CTS, U1RTS are disabled
U1MODEbits.WAKE = 1; // Wake-up on start bit is enabled
U1MODEbits.LPBACK = 0; // Loop-back is disabled
U1MODEbits.ABAUD = 0; // auto baud is disabled
U1MODEbits.RXINV = 0; // No RX inversion
U1MODEbits.BRGH = 0; // low boud rate
U1MODEbits.PDSEL = 0b00; // 8bit no parity
U1MODEbits.STSEL = 0; // one stop bit
U1STAbits.UTXISEL1 = 0b00;
U1STA &= 0xDFFF; // clear TXINV by bit masking
U1STAbits.UTXBRK = 0; // sync break tx is disabled
U1STAbits.UTXEN = 1; //transmit is enabled
U1STAbits.URXISEL = 0b00; // interrupt flag bit is set when RXBUF is filled whith 1 character
U1STAbits.ADDEN = 0; // address detect mode is disabled
U1STAbits.RIDLE = 0;
IPC2bits.U1RXIP = 7; // sET uart1 Priority to 7
IFS0bits.U1RXIF = 0; // clear interrupt flag of rx
IFS0bits.U1TXIF = 0; // clear interrupt flag of rx
IEC0bits.U1RXIE = 1; // enable rx recieved data interrupt
IEC0bits.U1TXIE = 0;
}
void delay(int delay)
{
__delay_ms(delay/2);
}
void UART4Init(void)
{
// U4BRG = 25; // 9600
U4BRG = 32; // 9600
U4MODEbits.UARTEN = 1; // UART2 is Enabled
U4MODEbits.USIDL = 0; // Continue operation at Idlestate
U4MODEbits.IREN = 0; // IrDA En/Decoder is disabled
U4MODEbits.RTSMD = 0; // flow control mode
U4MODEbits.UEN1 = 0b00; // UTX, RTX, are enabled U2CTS, U2RTS are disabled
U4MODEbits.UEN0 = 0b00; // UTX, RTX, are enabled U2CTS, U2RTS are disabled
U4MODEbits.WAKE = 1; // Wake-up on start bit is enabled
U4MODEbits.LPBACK = 0; // Loop-back is disabled
U4MODEbits.ABAUD = 0; // auto baud is disabled
U4MODEbits.RXINV = 0; // No RX inversion
U4MODEbits.BRGH = 0; // low boud rate
U4MODEbits.PDSEL = 0b00; // 8bit no parity
U4MODEbits.STSEL = 0; // one stop bit
U4STAbits.UTXISEL1 = 0b00;
U4STA &= 0xDFFF; // clear TXINV by bit masking
U4STAbits.UTXBRK = 0; // sync break tx is disabled
U4STAbits.UTXEN = 1; //transmit is enabled
U4STAbits.URXISEL = 0b00; // interrupt flag bit is set when RXBUF is filled whith 1 character
U4STAbits.ADDEN = 0; // address detect mode is disabled
IPC22bits.U4RXIP = 7; // sET uart1 Priority to 6
IFS5bits.U4RXIF = 0; // clear interrupt flag of rx
IFS5bits.U4TXIF = 0; // clear interrupt flag of rx
IEC5bits.U4RXIE = 1; // enAble rx recieved data interrupt
IEC5bits.U4TXIE = 0;
}
void UART1TransmitByte(uint8_t tx_byte)
{
U1TXREG = tx_byte;
while(!(U1STAbits.TRMT))
{
}
}
void UART1TransmitString(uint8_t *tx_str, uint16_t size)
{
_CNIE = 0;
uint8_t ch;
int i=0;
uint8_t temp = 0;
while (temp++<size)
{
ch = *tx_str;
U1TXREG = ch;
while(!(U1STAbits.TRMT))
{
}
tx_str++;
for(i=0;i<200;i++)
{
}
}
_CNIE = 1;
}
void UART4TransmitString(uint8_t *tx_str,uint16_t size)
{
_CNIE = 0;
uint8_t ch,i=0;
uart4_index = 0;
uint8_t temp = 0;
while (temp++<size)
{
ch = *tx_str;
U4TXREG = ch;
while(!(U4STAbits.TRMT))
{
}
tx_str++;
for(i=0;i<200;i++)
{
}
}
_CNIE = 1;
}
void __attribute__((interrupt,no_auto_psv)) _U1RXInterrupt()
{
char ch;
_U1RXIF = 0;
ch = U1RXREG;
gsm_buffer[gsm_index++]=ch;
if(gsm_index>300)
{
gsm_index=0;
}
}
void __attribute__((interrupt,no_auto_psv)) _U4RXInterrupt()
{
char ch4;
_U4RXIF = 0;
ch4 = U4RXREG;
uart4_buffer[uart4_index++]=ch4;
if(uart4_index>500)uart4_index=0;
}
void gsm_power_key()
{
delay(500);
PORTBbits.RB15 = 0;
__delay_ms(300);
PORTBbits.RB15 = 1;
__delay_ms(1000);
}
int gsm_cmd(uint8_t *atcmd,uint16_t delay1,int length)
{
memset(gsm_buffer,'\0',sizeof(gsm_buffer));
gsm_index = 0;
UART1TransmitString(atcmd,strlen(atcmd));
uint16_t temp=0;
while(gsm_index<length)
{
if(temp>=delay1)
{
UART4TransmitString(gsm_buffer,strlen(gsm_buffer));
return 0;
}
delay(1);
temp++;
}
UART4TransmitString(gsm_buffer,strlen(gsm_buffer));
}
void gsm_init()
{
gsm_cmd("AT\r\n",100,8); // //AT command
gsm_cmd("ATE1\r\n",300,11); //Set Command Echo Mode
gsm_cmd("ATI\r\n",300,27); //Display Product Identification Information
gsm_cmd("AT+CREG=1\r\n",300,27); //Display Product Identification Information
gsm_cmd("AT+CSQ\r\n",300,37); // Signal Quality Report
gsm_cmd("AT+COPS?\r\n",300,37); // Operator Selection
gsm_cmd("AT+CMGF=1\r\n",300,17); // Select SMS Message Format
gsm_cmd("AT+CPIN?\r\n",300,31); // Check SIM PIN
delay(500);
}
void gsm_time()
{
// gsm_cmd("AT+CCLK=\"27/06/21,12:20:12-32\"\r\n", 300,50);
gsm_cmd("AT+CCLK?\r\n", 300,50);
gsm_cmd("AT+CLTS=1\r\n",300,31); // Get Local Timestamp
gsm_cmd("AT&W\r\n",300,31); // Get Local Timestamp
gsm_cmd("AT+CCLK?\r\n", 300,50);
delay(500);
if(strstr((char *)gsm_buffer,"+CCLK:"))
{
memset(pkz,'\0',4);
sprintf(pkz,"%c%c",gsm_buffer[19],gsm_buffer[20]);
gsm_year=(atoi(pkz));
memset(pkz,'\0',4);
sprintf(pkz,"%c%c",gsm_buffer[22],gsm_buffer[23]);
gsm_month=(atoi(pkz));
memset(pkz,'\0',4);
sprintf(pkz,"%c%c",gsm_buffer[25],gsm_buffer[26]);
gsm_date=(atoi(pkz));
memset(pkz,'\0',4);
sprintf(pkz,"%c%c",gsm_buffer[28],gsm_buffer[29]);
gsm_hours=(atoi(pkz));
memset(pkz,'\0',4);
sprintf(pkz,"%c%c",gsm_buffer[31],gsm_buffer[32]);
gsm_minutes=(atoi(pkz));
memset(pkz,'\0',4);
sprintf(pkz,"%c%c",gsm_buffer[34],gsm_buffer[35]);
gsm_seconds=(atoi(pkz));
UART4TransmitString("GSM Date & Time :",sizeof("GSM Date & Time :"));
sprintf(GSM_TIME_DATE,"%02d.%02d.%02d : %02d/%02d/%02d\r\n",gsm_hours,gsm_minutes,gsm_seconds,gsm_date,gsm_month,gsm_year);
UART4TransmitString(GSM_TIME_DATE,sizeof(GSM_TIME_DATE));
}
}
int main(void)
{
gpio_init();
gsm_power_key();
delay(500);
UART1Init();
UART4Init();
delay(500);
UART4TransmitString("..............................\r\n",sizeof("..............................\r\n"));
UART4TransmitString("Start Application1\r\n",sizeof("Start Application1\r\n"));
UART4TransmitString("..............................\r\n",sizeof("..............................\r\n"));
delay(10500);
while(1)
{
gsm_init();
delay(5000);
gsm_time();
delay(1000);
}
return 0;
}
void gpio_init()
{
OSCCON = 0x0000;
OSCTUN = 0x0000;
CLKDIV = 0x0000;
//resetSource = RCON;
RCON = 0x00;
INTCON1bits.NSTDIS = 1;
AD1PCFGL = 0xFF; //dISABLE ANALOG I/P'S
//////// UART 1 /////////////
RPINR18bits.U1RXR = 6; // Assign U1RXR to RP6
_TRISB6 = 1; //CONFIGURE PIN TO I/P
RPOR3bits.RP7R = 3; //Assign U1TX To Pin RP7
_TRISB7 = 0; //CONFIGURE PIN TO O/P
//////// UART 2 /////////////
RPINR19bits.U2RXR = 8; // Assign U2RXR to RP8
_TRISB8 = 1; //CONFIGURE PIN TO I/P
RPOR4bits.RP9R = 5; //Assign U2TX To Pin RP9
_TRISB9 = 0; //CONFIGURE PIN TO O/P
//////// UART 3 /////////////
RPINR17bits.U3RXR = 3; // Assign U3RXR to RP3
_TRISD10 = 1; //CONFIGURE PIN TO I/P
RPOR0bits.RP0R = 28; //Assign U3TX To Pin RP0
_TRISB0 = 0; //CONFIGURE PIN TO O/P
//////// UART 4 /////////////
RPINR27bits.U4RXR = 23; // Assign U4RXR to RP23
_TRISD2 = 1; //CONFIGURE PIN TO I/P
RPOR12bits.RP24R = 30; //Assign U4TX To Pin RP24
_TRISD1 = 0; //CONFIGURE PIN TO O/P
CNPU1bits.CN9PUE = 1;
_TRISB15 = 0; // for modem reset
_TRISB13 = 0; // Relay
}
problems
When you enter AT+CCLK? Your not getting updated time and date
If your getting like this means your network time is not updated
What to do for that
- There is only one solution to update your current live Time and Date from GSM(SIM800)
- update your current date and time into gsm using the below command
- After that, you get the updated Time and Date
AT+CCLK=”21/06/27,13:14:00+22″
- But there is a problem with this update when you turn of the power you’re updated till will be zero
- But in over code, we updated AT+CCLK=1 when we get local updated Time and Date at that time this time will update with respected new local time.
- Because of some time AT+CCLK? take time to update local time.
Why it is not updating
- Your AT+CCLK? not providing the current Date and Times because you don’t have proper signal strength.
- On the other hand AT+COPS? The operator name is not found in your gsm module check your AT+COPS?
- in case you’re getting the operator name then you’re not going to face any kind of issue.
Output
